1. FIELD OF THE INVENTION
This invention relates generally to RF signal generators and radiators therefor and more particularly to a sub-nanosecond, kilovolt pulse generator including a transmitting antenna integrated therewith for use in impulse radar apparatus, active electromagnetic signal jammers, and relatively high power microwave weapon systems.
2. DESCRIPTION OF THE PRIOR ART
Recently there has been much research activity into the generation and radiation of high power video pulses with sub-nanosecond risetimes. This stems from its ability to couple into and upset other electronic systems. Since the radiated power diminishes according to the inverse of square of distance between the radiating source and the target, a fast risetime is essential for the penetration of electronic systems having protective mechanisms. A high power, fast risetime RF source, combined with a wide bandwidth radiating element therefor becomes a much needed piece of equipment for future military systems such as active jammers and impulse radars.
In the above cross referenced related application, there is disclosed a sub-nanosecond pulse generator using a radial transmission line comprised of a photoconductive bulk GaAs switch centrally embedded in a circular dielectric disc of constant thickness with radial type layers of metallization formed on top and bottom surfaces thereof.
Since the characteristic impedance of such a device is inversely proportional to the width of the dielectric separating the top and bottom layers of metallization, the radial transmission line creates a non-uniform characteristic impedance primarily due to its geometrical configuration. Therefore, at a location outward from the center of the radial transmission line, the impedance is smaller compared to that at a closer in location. When the radial transmission line is charged and the photoconductive switch is optically activated, traveling waves begin to flow from the outer low impedance region to the inner high impedance region and in the process a voltage transformation occurs. Thus one of the advantages of this type of pulser is its property to produce voltage amplitude enhancement of the signal coupled to the load. Although this pulser can be connected to a conventional antenna via a waveguide, this invention contemplates integrating the antenna into the pulser itself.